1. Field of the Invention
The present invention relates to a light-emitting device, and more particularly, to an alternating current light emitting device and the fabrication method thereof.
2. Description of Related Art
Unlike white light which is a mixture of different colors, light emitting diodes (LEDs) emit monochromatic light by applying electric current to a radiating material to produce a light described as a cold light since it is produced at a relatively low temperature. Due to the superiority of light emitting diodes in terms of their relative high durability, longevity, portability, low power consumption, absence of harmful substances such as mercury, and so forth, the development of LED-based solid state lighting has become one of the crucial research targets for the global lighting industry as well as the semiconductor industry. Often-seen applications of LEDs include white light illumination (using red, blue, and green LEDs), indicator lights, vehicle signal and illuminating lights, flash lights, LED back-light modules, projector light sources, outdoor displays, and so forth.
White light devices, among the most important lighting applications, still require a patented fabrication process involving fluorescent light. In addition to the necessity of paying royalties, drawbacks include the distribution ratio of fluorescent light and the high color temperature of white light generated by a packaging fabrication process that can lead to decreased operating life and loss of efficacy as a result of the high temperature. Moreover, difficulties in controlling the conventional packaging technique lead to low yield.
Taiwanese Patent Application No. 093126201 discloses a light emitting diode (LED) chip structure having an alternating current circuit, the patent comprising at least one alternating current micro diode LED module formed on a chip and comprised of two micro diode LEDs having a reverse positive/negative parallel connection so as to apply alternating current thereto, such that two micro diode LEDs can, working in turn, emit light during both the positive and negative half cycles of the AC waveform to overcome the drawback of the prior art technique in which devices utilizing that technique emit light during only the positive half cycle but not during the negative half cycle. The invention thereby achieves the objective of fully utilizing alternating current as a power source to significantly expand and upgrade applications of LED elements.
In the foregoing patent, due to the plane array configuration adopted, each micro diode can only emit light during an alternating current half cycle in which the current is flowing in the same direction. In other words, at any particular moment, only half the area of the chip surface can emit light and micro diodes on the other half of the chip surface are non-luminous in an off status. Therefore, in order to obtain the same amount of light that could be obtained if the device constantly emitted light during both half cycles, the amount of electric current has to be doubled.
Further, the micro diode disclosed by said patent has an isosceles, right-angle triangular shape with legs of an approximate length of 70 micrometers each. The design process is difficult if it is necessary to reduce the size of the LEDs to comply with the application trend for product miniaturization. Furthermore, since this patent requires the application of patented sun-second fluorescent powder, the foregoing drawbacks of high color temperature and a hard-to-control packaging process still exist.
Therefore, a need exists to develop a novel alternating current light emitting device that not only improves on the drawbacks of the prior art, but also provides a full-scale light emitting area so as to evenly emit light full time in a way that can be controlled at low color temperature while also exhibiting a higher overlapping area without requiring the use of patented sun-second fluorescent power, thereby decreasing the fabrication difficulties and increasing yield to further enhance the industrial applicability.